<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta content="IE=edge" http-equiv="X-UA-Compatible">
    <meta content="width=device-width, initial-scale=1.0" name="viewport">
    <title>Document</title>

</head>
<body>
<div id="app">
    <button @click.once="fn">按钮</button>
</div>
<script src="./vue.js"></script>
<script>

    const vm = new Vue({
        el: '#app',
        data: {},
        methods: {
            fn() {
                alert(1)
            }
        }
    })


</script>
</body>
</html>